1. Field of the Invention
The present invention relates to an image processing system.
2. Description of the Prior Art
There is already known a system for reading data from an original document and converting said data into binary output data.
The present applicant has already proposed an image processing system for reading an original image with plural CCD's, in which, in order to avoid positional aberration or overlapping of the image data at the junctions of said CCD's, a black sample marker is read in advance and the resulting binary data indicating the position of the marker are utilized for correcting the image data of the original document.
The present applicant has also proposed an image processing system capable of a process for recognizing the position and dimension of the original image by the CCD's for reading the original document. In this system the recognition of the position and dimension of the original image is conducted after the image data obtained by image reading are binary encoded.
In these systems, however, there may result drawbacks, explained in the following, if a threshold value for binary encoding for image reproduction of the image data obtained by reading the original document is utilized also for binary encoding of the data obtained by reading the sample marker for the correction of the junctions of CCD's.
More specifically the precision of such junction correction may be caused to deteriorate, at the sample marker reading, by a stain or a smear on a white board bearing the black marker. Particularly in the case that the threshold value for binary encoding is selected low in order to enable binary encoding of an original image of low density, such a stain may be erroneously identified as the marker. On the other hand, if said threshold value is selected high in order not to reproduce the background of the original image, the marker may not be recognized properly.
Also, if the threshold value for binary encoding, for the purpose of image reproduction, the data obtained by reading the original image is utilized for conducting the process for recognizing the position and dimension of the original image, there will result a limitation on the recognizable original images. More specifically, if the threshold value is selected at the approximate middle between black and white levels, it becomes impossible to distinguish a document with a colored background such as blue from other areas.
Also, for the purpose of reproducing a half-tone image, the image data obtained by reading the original image may be subjected to a dither process in which the image data are periodically compared with binary encoding threshold levels. In such a case the precision of the aforementioned junction correction or of the document recognition may be caused to deteriorate depending on the dither pattern or the threshold levels of the dither elements.